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Abstract

Anorganic preparations of the distal metaphyseal and epiphyseal regions of the femoral bones from young male rats given 150 ppm fluoride in the drinking water for 10 weeks were examined by scanning electron microscopy. Longitudinal sections of the bones revealed an increase in the zone of mature hypertrophied cells of the epiphyseal plates as compared with controls. The lacunae in this zone varied considerably in size and shape, and were arranged in irregular nests rather than in parallel rows. Within the cavity of the shaft, the amount of cancellous bone was reduced, particularly in the central areas of the metaphyses where the network of trabeculae was sparsely distributed. The trabeculae located in the more peripheral areas of the metaphyses were broad and heavy in appearance. Areas of fully or partially mineralized bone were markedly reduced. The bone surfaces were rough, irregular and covered with numerous Howship's lacunae. The results of this investigation indicate that the initial effects of fluoride on bone include an inhibition of resorption in the epiphyseal plate coupled with an increase in resorption of metaphyseal trabecular bone.